As the eyes are enclosed organs with slow blood circulation, most therapeutic agents cannot reach them in effective amounts when administered systemically.
To resolve this problem, intravitreal injection has been adopted for ophthalmic delivery of therapeutic agents, particularly to the rear ends of the eyes (e.g., retina and choroid). As a therapeutic agent typically stays in the eyes for a limited period, repetitive intravitreal injections are required to achieve the intended therapeutic effect. However, frequent administration using this invasive approach is highly undesirable.
There is a need for a drug delivery system that prolongs the lifetime of a therapeutic agent in the eyes so as to reduce the times of intravitreal injection required in a treatment.